U.S. patent application number 16/075853 was filed with the patent office on 2019-01-31 for semiconductor light source.
The applicant listed for this patent is OSRAM Opto Semiconductors GmbH. Invention is credited to Christoph Eichler, Alfred Lell, Andreas Loffler, Bernhard Stojetz.
Application Number | 20190036303 16/075853 |
Document ID | / |
Family ID | 58358567 |
Filed Date | 2019-01-31 |
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United States Patent
Application |
20190036303 |
Kind Code |
A1 |
Stojetz; Bernhard ; et
al. |
January 31, 2019 |
Semiconductor Light Source
Abstract
A semiconductor light source is disclosed. In one embodiment, a
semiconductor light source includes at least one semiconductor
laser for generating a primary radiation and at least one
conversion element for generating a longer-wave visible secondary
radiation from the primary radiation, wherein the conversion
element for generating the secondary radiation comprises a
semiconductor layer sequence having one or more quantum well
layers, and wherein, in operation, the primary radiation is
irradiated into the semiconductor layer sequence perpendicular to a
growth direction thereof, with a tolerance of at most
15.degree..
Inventors: |
Stojetz; Bernhard; (Wiesent,
DE) ; Lell; Alfred; (Maxhutte-Haidhof, DE) ;
Eichler; Christoph; (Donaustauf, DE) ; Loffler;
Andreas; (Neutraubling, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OSRAM Opto Semiconductors GmbH |
Regensburg |
|
DE |
|
|
Family ID: |
58358567 |
Appl. No.: |
16/075853 |
Filed: |
March 13, 2017 |
PCT Filed: |
March 13, 2017 |
PCT NO: |
PCT/EP2017/055823 |
371 Date: |
August 6, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01S 5/309 20130101;
H01S 5/2228 20130101; H01L 33/18 20130101; F21K 9/64 20160801; H01S
5/3408 20130101; F21Y 2115/30 20160801; H01L 33/502 20130101; H01S
5/0609 20130101; H01L 33/507 20130101 |
International
Class: |
H01S 5/06 20060101
H01S005/06; H01S 5/22 20060101 H01S005/22; H01S 5/30 20060101
H01S005/30; H01S 5/34 20060101 H01S005/34; F21K 9/64 20060101
F21K009/64 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2016 |
DE |
10 2016 104 616.7 |
Claims
1-16. (canceled)
17. A semiconductor light source comprising: at least one
semiconductor laser for generating a primary radiation; and at
least one conversion element for generating a longer-wave visible
secondary radiation from the primary radiation, wherein the
conversion element for generating the secondary radiation comprises
a semiconductor layer sequence having one or more quantum well
layers, and wherein, in operation, the primary radiation is
irradiated into the semiconductor layer sequence perpendicular to a
growth direction thereof, with a tolerance of at most
15.degree..
18. The semiconductor light source according to claim 17, wherein
the quantum well layers are three-dimensionally shaped so that the
quantum well layers have kinks when viewed in cross section and are
oriented at least in places obliquely to the growth direction of
the semiconductor layer sequence.
19. The semiconductor light source according to claim 17, wherein a
main radiation direction of the semiconductor light source is
oriented parallel to the growth direction, with a tolerance of at
most 15.degree., and an emission angle range has a half-width of at
most 90.degree., and wherein the semiconductor laser and the
conversion element are grown epitaxially independently of one
another and do not touch each other.
20. The semiconductor light source according to claim 17, wherein,
in operation, the primary radiation is irradiated into the
semiconductor layer sequence perpendicular to the growth
direction.
21. The semiconductor light source according to claim 17, wherein
the semiconductor laser emits the primary radiation in a
line-shape, wherein the semiconductor laser is arranged such that a
growth direction of the semiconductor laser is oriented
perpendicular to the growth direction of the semiconductor layer
sequence, and wherein the primary radiation reaches the
semiconductor layer sequence in a free-beam manner from the
semiconductor laser.
22. The semiconductor light source according claim 17, wherein, in
operation, the primary radiation is irradiated into the
semiconductor layer sequence parallel to a growth direction
thereof, with a tolerance of at most 15.degree., and wherein the
semiconductor layer sequence is homogeneously illuminated with the
primary radiation.
23. The semiconductor light source according to claim 17, wherein
the conversion element has a continuous base region and
semiconductor columns extending away from the base region, and
wherein the semiconductor columns serve as waveguides for the
primary radiation in the direction parallel to the growth direction
of the semiconductor layer sequence.
24. The semiconductor light source according to claim 23, wherein
the quantum well layers are arranged on the semiconductor columns,
wherein an emission of at least one of the secondary radiation and
of the primary radiation from the semiconductor columns occurs to
at least 50% on tips of the semiconductor columns.
25. The semiconductor light source according to claim 23, wherein
the semiconductor columns have an average diameter of between 0.5
.mu.m and 20 .mu.m inclusive, and a ratio of a mean height of the
semiconductor columns and the average diameter is between 3 and 26
inclusive.
26. The semiconductor light source according to claim 17, wherein
the quantum well layers are pyramid shaped or are composed of
pyramid shapes, and wherein the quantum well layers are surrounded
by further layers of the semiconductor layer sequence on two main
sides lying opposite one another.
27. The semiconductor light source according to claim 17, wherein
the quantum well layers are configured to generate different
wavelengths of the secondary radiation, and wherein a spectral
half-width of the secondary radiation, which is generated by the
quantum well layers, is at least 60 nm.
28. The semiconductor light source according to claim 17, wherein
the conversion element additionally comprises at least one luminous
material.
29. The semiconductor light source according to claim 28, wherein
the luminous material is doped with at least one rare earth.
30. The semiconductor light source according to claim 28, wherein
the luminous material is selected from the group consisting
essentially of oxide, nitride, oxynitride, garnet, sulfide,
silicate, phosphate and halide.
31. The semiconductor light source according to claim 17, wherein
an emission surface of the semiconductor laser for the primary
radiation is smaller by at least a factor of 100 than an emission
surface of the conversion element for the secondary radiation.
32. The semiconductor light source according to claim 17, wherein,
in the direction perpendicular to the growth direction, the
semiconductor layer sequence is as a waveguide for the primary
radiation.
33. The semiconductor light source according to claim 17, wherein
the primary radiation does not leave the semiconductor light source
during operation, and wherein a wavelength of maximum intensity of
the primary radiation is between 360 nm and 490 nm inclusive.
34. The semiconductor light source according to claim 17, wherein
the at least one semiconductor laser and the at least one
conversion element are monolithically integrated.
35. A semiconductor light source comprising at least one
semiconductor laser for generating a primary radiation; and at
least one conversion element for generating a longer-wave visible
secondary radiation from the primary radiation, wherein the
conversion element for generating the secondary radiation comprises
a semiconductor layer sequence having one or more quantum well
layers.
Description
[0001] This patent application is a national phase filing under
section 371 of PCT/EP2017/055823, filed Mar. 13, 2017, which claims
the priority of German patent application 10 2016 104 616.7, filed
Mar. 14, 2016, each of which is incorporated herein by reference in
its entirety.
TECHNICAL FIELD
[0002] A semiconductor light source is specified.
SUMMARY OF THE INVENTION
[0003] Embodiments provide a semiconductor light source which emits
radiation that can be directed efficiently into a specific spatial
region and can be adjusted in different colors.
[0004] According to at least one embodiment, the semiconductor
light source comprises one or more semiconductor lasers for
generating a primary radiation. In this case, it is possible to use
a plurality of structurally identical semiconductor lasers or also
a plurality of different semiconductor lasers, in particular,
having different emission spectra. The semiconductor light source
preferably comprises exactly one semiconductor laser.
[0005] According to at least one embodiment, the primary radiation,
which is generated by the at least one semiconductor laser during
operation, is ultraviolet radiation or visible light. For example,
a wavelength of maximum intensity is at least 250 nm or 320 nm or
360 nm or 400 nm or 440 nm and/or at most 570 nm or 535 nm or 525
nm or 490 nm or 420 nm. In particular, the wavelength of maximum
intensity of the primary radiation is 375 nm or 405 nm or 450 nm,
in each case with a tolerance of at most 10 nm.
[0006] According to at least one embodiment, the semiconductor
light source comprises one or more conversion elements. The at
least one conversion element is designed to generate a longer-wave
visible secondary radiation from the primary radiation. In other
words, the conversion element converts the primary radiation
completely or partially into the secondary radiation. In the
intended use, the secondary radiation is emitted from the
semiconductor light source and is perceived by a user.
[0007] According to at least one embodiment, the conversion element
has a semiconductor layer sequence for generating the secondary
radiation. The semiconductor layer sequence comprises one or more
quantum well layers. The primary radiation is absorbed in the at
least one quantum well layer and converted into the secondary
radiation via charge carrier recombination. In other words, the
quantum well layers are excited to photoluminescence by the primary
radiation and thus optically pumped.
[0008] According to at least one embodiment, the quantum well
layers are of a three-dimensional shape. This can mean that the
quantum well layers or at least one of the quantum well layers or
all quantum well layers, in particular when viewed in cross
section, have one or more kinks. The quantum well layers or at
least some of the quantum well layers are then, viewed in cross
section, not configured as uninterrupted straight lines.
[0009] According to at least one embodiment, at least one, some or
all of the quantum well layers, viewed in cross section, are
arranged in places or completely obliquely to a growth direction of
the semiconductor layer sequence of the conversion element. In
other words, the quantum well layers are oriented neither parallel
nor perpendicular to the growth direction, at least in certain
regions or even entirely.
[0010] According to at least one embodiment, at least one, some or
all of the quantum well layers, viewed in cross section, are
arranged in places or completely perpendicular to the growth
direction of the semiconductor layer sequence of the conversion
element. The respective quantum well layers can be restricted to
the base regions and can be designed as continuous layers, or can
be located only within the semiconductor columns, or else both.
[0011] In at least one embodiment, the semiconductor light source
comprises at least one semiconductor laser for generating a primary
radiation and at least one conversion element for generating a
longer wavelength, visible secondary radiation from the primary
radiation. In order to generate the secondary radiation, the
conversion element has a semiconductor layer sequence having one or
more quantum well layers. The quantum well layers are preferably
shaped three-dimensionally, so that the quantum well layers have
kinks when viewed in cross section and/or are oriented at least in
places obliquely to a growth direction of the semiconductor layer
sequence.
[0012] In the semiconductor light source described here, an
efficient, radiation-generating semiconductor laser can be used as
a light source for the primary radiation. By means of the
conversion element, in the case of a specific semiconductor laser
for generating the primary radiation, an emission wavelength range
can be set by using quantum well layers that can be configured
differently. By using photoluminescent quantum well layers in the
conversion element, a high conversion efficiency can be achieved
and the desired spectral properties of the secondary radiation can
be specifically set by a design of the quantum well layers. A
highly efficient, colored semiconductor light source, which can
also be scaled in size, can thus be achieved, in particular with a
directional emission characteristic.
[0013] In contrast, other scalable light sources having a
directional emission characteristic such as vertically emitting
semiconductor lasers, that is to say with semiconductor lasers
which emit in the direction parallel to a growth direction, have
only a low efficiency. Light sources having nanostructures and
having a phosphor conversion layer likewise have a comparatively
low conversion efficiency and cause difficulties in electrical
contacting and when coupling out light. White light-emitting laser
diodes which are provided with a phosphor require, as a rule, a
complex optical system in order to focus and efficiently couple
light out of the phosphor. Thus, such alternative solutions have a
low component efficiency and a relatively low conversion
efficiency, as well as a more complex design, for instance with
regard to electrical contacting or optics.
[0014] According to at least one embodiment, a main emission
direction of the semiconductor light source is oriented parallel to
the growth direction of the semiconductor layer sequence of the
conversion element, with a tolerance of at most 15.degree. or
10.degree. or 5.degree.. An emission angle range of the conversion
element has a half-width of at most 90.degree. or 70.degree., so
that light is emitted more directional by the conversion element
than in the case of a Lambertian emitter. In the case of a
Lambertian emitter, the following applies to an intensity I as a
function of an angle .alpha. and relative to a maximum intensity
I.sub.max: I(.alpha.)=I.sub.max cos .alpha.. In the case of a
Lambertian emitter, the half-width of the emission characteristic
is thus substantially greater.
[0015] According to at least one embodiment, the semiconductor
laser and the conversion element are grown epitaxially
independently of one another. That is to say that the semiconductor
laser and the conversion element are two components produced
independently of one another, which are only combined in the
semiconductor light source.
[0016] According to at least one embodiment, the conversion element
and the semiconductor laser do not touch each other. This can mean
that an intermediate region with a different material is present
between the semiconductor laser and the conversion element. The
intermediate region is, for example, gas-filled or evacuated or
bridged by a light guide or a transparent body such as a
transparent semiconductor material.
[0017] According to at least one embodiment, in operation the
primary radiation is irradiated into the semiconductor layer
sequence perpendicular to the growth direction, with a tolerance of
at most 15.degree. or 10.degree. or 5.degree. or 1.degree.. In
other words, the irradiation direction of the primary radiation can
be oriented perpendicular to the main emission direction of the
conversion element. If, for example, the semiconductor laser has a
Gaussian beam profile when viewed in a cross section, the emission
direction of the semiconductor laser thus relates to the direction
of maximum intensity. This can apply correspondingly to other
emission profiles of the primary radiation.
[0018] According to at least one embodiment, the primary radiation
is emitted in a linear shape by the semiconductor laser or in an
elliptical emission characteristic or elliptical angular
distribution or also linearly. This can mean that an aspect ratio
of a width and a length of the primary radiation, in particular
seen in the optical far field, is at least 2 or 5 or 10 or 50. A
uniform illumination of the semiconductor layer sequence of the
conversion element can be achieved by such a line profile of the
primary radiation.
[0019] According to at least one embodiment, the semiconductor
laser is arranged such that a growth direction of the semiconductor
laser is oriented perpendicular to the growth direction of the
semiconductor layer sequence. In this case, the growth direction of
the semiconductor laser is preferably parallel to a plane which is
defined by the semiconductor layer sequence. In other words, the
growth direction of the semiconductor laser is oriented
perpendicular to the growth direction of the semiconductor layer
sequence and thus parallel to a plane to which the growth direction
of the semiconductor layer sequence is perpendicular. This applies
in particular to a tolerance of at most 10.degree. or 5.degree. or
1.degree.. Furthermore, the growth direction of the semiconductor
laser is preferably oriented perpendicular to the emission
direction of the semiconductor laser, which in turn can be oriented
perpendicular to the growth direction of the semiconductor layer
sequence of the conversion element.
[0020] According to at least one embodiment, the semiconductor
laser is a so-called stripe laser, also referred to as a ridge
laser. In this case, the semiconductor laser comprises at least one
ridge which is produced from a semiconductor layer sequence of the
semiconductor laser and which serves as a waveguide for the primary
radiation within the semiconductor laser.
[0021] According to at least one embodiment, during operation, the
primary radiation is irradiated into the semiconductor layer
sequence of the conversion element parallel to the growth direction
of the semiconductor layer sequence, with a tolerance of at most
10.degree. or 5.degree. or 1.degree.. In this case, an emission
direction of the semiconductor laser can be oriented parallel to
the main emission direction of the conversion element. If both
primary radiation and secondary radiation are emitted from the
semiconductor light source, it is possible that a direction of the
primary radiation is not or not significantly changed after leaving
the semiconductor laser.
[0022] According to at least one embodiment, the conversion element
has a base region. The base region is preferably a continuous,
uninterrupted region of the semiconductor layer sequence of the
conversion element. In particular, the base region extends
perpendicular to a growth direction of the semiconductor layer
sequence. It is possible for the base region to be free of quantum
well layers. Alternatively, the quantum well layers can be located
in the base region.
[0023] According to at least one embodiment, the conversion element
comprises a plurality of semiconductor columns. The semiconductor
columns preferably extend away from the base region, in the
direction parallel to the growth direction of the semiconductor
layer sequence.
[0024] According to at least one embodiment, the semiconductor
layer sequence, in particular the base region, works as a waveguide
for the primary radiation within the conversion element. In
particular, the semiconductor layer sequence and/or the base region
is/are designed as a waveguide in the direction perpendicular to
the growth direction of the semiconductor layer sequence.
[0025] According to at least one embodiment, the semiconductor
columns, as waveguides for the primary radiation, are aligned along
the direction parallel to the growth direction and in particular
also along the direction parallel to the main emission direction of
the conversion element. Thus, by means of the semiconductor
columns, an emission characteristic and especially the main
emission direction of the conversion element can be determined. The
semiconductor columns are preferably not a photonic crystal. The
semiconductor columns differ from a photonic crystal in particular
by means of larger geometric dimensions and by an irregular or less
regular arrangement.
[0026] According to at least one embodiment, the primary radiation
passes from the semiconductor laser in a free-beam manner to the
semiconductor layer sequence. This can mean that there are no
optics for the primary radiation between the semiconductor layer
sequence and the semiconductor laser and/or a region between the
semiconductor laser and the semiconductor layer sequence is
completely or predominantly evacuated or filled with a gas.
Predominantly can mean that an optical path between the
semiconductor laser and the semiconductor layer sequence is at
least 50% or 70% or 90% free of condensed matter.
[0027] According to at least one embodiment, the at least one
quantum well layer is applied to and/or on the semiconductor
columns. In this case, the quantum well layers can imitate a shape
of the semiconductor columns. In particular, the semiconductor
columns form a core and the quantum well layers form a mantle. Such
a structure is also referred to as a core-shell structure.
[0028] Any kinks in the quantum well layers, which may be present
in cross section, can result, for example, from the quantum well
layers from side surfaces of the semiconductor columns bending in
the direction towards an upper side of the semiconductor columns
and optionally also bending back towards an opposite side surface.
The quantum wells can follow a crystal structure of the underlying
layers and/or of the rods.
[0029] According to at least one embodiment, the secondary
radiation and/or the primary radiation is/are radiated out of the
semiconductor columns to at least 50% or 70% or 85% at the tips of
the semiconductor columns. In other words, regions between the
semiconductor columns and side faces of the semiconductor columns
are dark or significantly darker, especially in comparison to the
tips of the semiconductor columns.
[0030] According to at least one embodiment, the semiconductor
columns have an average diameter of at least 0.5 .mu.m or 0.7 .mu.m
or 1 .mu.m. Alternatively or additionally, the average diameter is
at most 10 .mu.m or 4 .mu.m or 3 .mu.m.
[0031] According to at least one embodiment, a ratio of a mean
height and the mean diameter of the semiconductor columns is at
least 2 or 3 or 5 and/or at most 20 or 10 or 7 or 5. By such a
ratio of height and diameter, the semiconductor columns can serve
as waveguides for the primary radiation in the direction parallel
to the main emission direction.
[0032] According to at least one embodiment, the quantum well
layers are shaped like pyramid shells or assembled from a plurality
of pyramid shells. In other words, the quantum well layers can be
designed similarly to an egg carton or napped foam. In this case,
the quantum well layers are preferably shaped like hexagonal
pyramids, in particular as viewed as a relief.
[0033] According to at least one embodiment, the quantum well
layers are surrounded by further layers of the semiconductor layer
sequence on two opposing main sides. In other words, the quantum
well layers can be embedded in the semiconductor layer sequence so
that the quantum well layers do not represent any outer layers of
the semiconductor layer sequence. The further layers are, for
example, cladding layers having a relatively low refractive index
to enable a wave guidance of the primary radiation in the direction
perpendicular to the growth direction of the semiconductor layer
sequence.
[0034] According to at least one embodiment, the quantum well
layers are designed to generate different wavelengths of the
secondary radiation. In this case, the different wavelengths can be
generated in different regions along the growth direction or in
different regions parallel to the growth direction. For example,
quantum well layers are provided for generating blue light and/or
green light and/or yellow light and/or red light.
[0035] According to at least one embodiment, a spectral half-width
of the secondary radiation, which is generated by the quantum well
layers, is at least 40 nm or 60 nm or 80 nm. Thus, the secondary
radiation is in particular mixed-colored light, for example, white
light. According to at least one embodiment, the conversion element
comprises one or more further luminous materials in addition to the
quantum well layers, preferably inorganic phosphors. The luminous
material specified in the publication EP 2 549 330 A1 or else
quantum dots can be used as phosphors. The at least one luminous
material can be one or more of the following substances:
Eu.sup.2+-doped nitrides such as (Ca,Sr)AlSiN.sub.3:Eu.sup.2+,
Sr(Ca,Sr)Si.sub.2Al.sub.2N.sub.6:Eu.sup.2+,
(Sr,Ca)AlSiN.sub.3*Si.sub.2N.sub.2O:Eu.sup.2+,
(Ca,Ba,Sr).sub.2Si.sub.5N.sub.8:Eu.sup.2+,
(Sr,Ca)[LiA1.sub.3N.sub.4]:Eu.sup.2+; garnets from the general
system (Gd,Lu,Tb,Y).sub.3(Al,Ga,D).sub.5(O,X).sub.12:RE where
X=halide, N or divalent element, D=three-or four-valent element and
RE=rare earth metals, such as
Lu.sub.3(Al.sub.1-xGa.sub.x).sub.5O.sub.12:Ce.sup.3+,
Y.sub.3(Al.sub.1-xGa.sub.x).sub.5O.sub.12:Ce.sup.3+;
Eu.sup.2+-doped SiONs such as
(Ba,Sr,Ca)Si.sub.2O.sub.2N.sub.2:Eu.sup.2+; SiAlONs e.g. from the
system
Li.sub.xM.sub.yLn.sub.zSi.sub.12-(m+n)Al.sub.(m+n)O.sub.nN.sub.16-n;
orthosilicates such as (Ba,Sr,Ca,Mg).sub.2SiO.sub.4:Eu.sup.2+.
[0036] According to at least one embodiment, an emission surface of
the semiconductor laser for the primary radiation is smaller by at
least a factor of 10 or 100 or 1000 than an emission surface of the
conversion element for the secondary radiation and/or the primary
radiation. In other words, an enlargement of an emission surface,
relative to the emission surface of the semiconductor laser, takes
place in the conversion element.
[0037] According to at least one embodiment, the primary radiation
does not leave the semiconductor light source during its intended
use. In this case, the primary radiation is preferably completely
or substantially completely converted into the secondary radiation.
An additional filter layer can be located on a light exit side of
the conversion element, the filter layer prevents the primary
radiation from leaving the semiconductor light source.
[0038] According to at least one embodiment, the primary radiation
is only partially converted into the secondary radiation. This
means, in particular, that a mixed radiation is emitted by the
semiconductor light source, which is composed of the primary
radiation and of the secondary radiation. A power proportion of the
primary radiation on the mixed radiation is preferably at least 10%
or 15% or 20% and/or at most 50% or 40% or 30%.
[0039] According to at least one embodiment, the at least one
semiconductor laser and the at least one conversion element are
monolithically integrated. This can mean that the semiconductor
laser and the conversion element are grown on the same growth
substrate and are preferably still located on the growth substrate.
This can likewise mean that the semiconductor laser and the
conversion element are formed from a contiguous semiconductor layer
sequence.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] A semiconductor light source described here is explained in
more detail below with reference to the drawing on the basis of
exemplary embodiments. Identical reference signs indicate the same
elements in the individual figures. In this case, however, no
relationships to scale are illustrated; rather, individual elements
can be represented with an exaggerated size in order to afford a
better understanding.
[0041] In the figures:
[0042] FIGS. 1 to 18 show schematic sectional representations of
exemplary embodiments of semiconductor light sources;
[0043] FIG. 19 shows a schematic perspective illustration of an
exemplary embodiment of a semiconductor light source; and
[0044] FIGS. 20A to 20F show schematic sectional representations of
tips of semiconductor columns for exemplary embodiments of
semiconductor light sources.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0045] FIG. 1 shows an exemplary embodiment of a semiconductor
light source 1. The semiconductor light source 1 comprises a
semiconductor laser 2 having an active zone 22. The semiconductor
laser 2 has a growth direction H. A primary radiation P exits from
the semiconductor laser 2 at a light exit region 20 and is emitted
towards a conversion element 3. The primary radiation P is
generated by means of electroluminescence.
[0046] The conversion element 3 of the semiconductor light source 1
contains a semiconductor layer sequence 30 which is optionally
located on a growth substrate 38. A growth direction G of the
semiconductor layer sequence 30 can be oriented parallel to the
growth direction H of the semiconductor laser 2.
[0047] The semiconductor layer sequence 30 comprises a base region
33 and a multiplicity of semiconductor columns 34 in the base
region 33, the primary radiation P is guided in the direction
perpendicular to the growth direction G of the semiconductor layer
sequence 30. A uniform distribution of the primary radiation P
across the conversion element 3 can be achieved by means of the
base region 33. The semiconductor columns 34 extend from the base
region 33. Quantum well layers 31 are grown on the semiconductor
columns 34. The quantum well layers 31 represent envelopes to the
semiconductor columns 34. Optionally, the quantum wells 31 are
covered by a further semiconductor layer 36 or also by a protective
layer, not shown.
[0048] The semiconductor layer sequence is preferably based on a
nitride compound semiconductor material such as
Al.sub.nIn.sub.1-n-mGa.sub.mN or on a phosphide compound
semiconductor material Al.sub.nIn.sub.1-n-mGa.sub.mP or else on an
arsenide compound semiconductor material such as
Al.sub.nIn.sub.1-n-mGa.sub.mAs or as
Al.sub.nGa.sub.mIn.sub.1-n-mAs.sub.kP.sub.1-k, wherein in each case
o.ltoreq.n.ltoreq.1, o.ltoreq.m.ltoreq.1 and n+m.ltoreq.1 and
o.ltoreq.k<1. Preferably, the following applies to at least one
layer or for all layers of the semiconductor layer sequence
o<n.ltoreq.0.8, 0.4.ltoreq.m<1 and n+m.ltoreq.0.95 and
o<k.ltoreq.0.5. The semiconductor layer sequence can have
dopants and additional components. For the sake of simplicity,
however, only the essential components of the crystal lattice of
the semiconductor layer sequence are mentioned, that is, Ga, In, N
or P, even if these can be partially replaced and/or supplemented
by small quantities of further substances. The semiconductor layer
sequence is preferably based on Al.sub.nIn.sub.1-n-mGa.sub.mN, as
in all other exemplary embodiments.
[0049] The semiconductor columns 34 form a waveguide for the
primary radiation P in the direction parallel to the growth
direction G. The primary radiation P exits the semiconductor
columns 34 at tips 35 of the semiconductor columns 34, passes
through the quantum well layers 31 and is converted into a
secondary radiation S. A mixture of the secondary radiation S and
the primary radiation P is thus emitted at the tips 35.
Alternatively, it is possible for only the secondary radiation S to
emerge from the conversion element 3.
[0050] Both the semiconductor laser 2 and the conversion element 3
are located on a common carrier 4, which can also contain further
electronic components (not shown), for example, for controlling the
semiconductor laser 2.
[0051] According to FIG. 1, the tips 35 of the semiconductor
columns 34 are of pyramid-shaped design, for example, as hexagonal
pyramids. Seen in cross section, the quantum well layers 31
therefore have kinks. Unlike in FIG. 1, it is also possible for the
quantum well layers 31 to be restricted only to the tips 35 so that
a region between the semiconductor columns 34 and/or side surfaces
of the semiconductor columns 34 is then free of the quantum well
layers 31.
[0052] The conversion element 3 is a structure similar to an LED,
wherein electrical contact layers and current spreading layers can
be dispensed with, since the secondary radiation S is generated by
photoluminescence. Through the quantum well layers, for example, by
the thickness and/or material composition thereof, a wavelength of
the secondary radiation S can be set in a targeted manner over a
wide range. Since no electrical contact layers or current spreading
layers need to be present, an efficiency of the photoluminescence
can be increased compared to electroluminescence in a conventional
light-emitting diode. Furthermore, a base area of the conversion
element is substantially freely scalable. In addition, a light
intensity of the semiconductor light source 1 can be set by using
different and/or a plurality of semiconductor lasers 2.
[0053] In other words, the primary radiation P, which is laser
radiation, is coupled into the conversion element 3 as a
beam-shaping element, for instance into a lateral chip flank of an
LED chip on the basis of the material system InGaN with a sapphire
growth substrate 38. The conversion element 3 contains a waveguide
with an optically active coupling-out structure, formed by the
semiconductor columns 34. The primary radiation P couples into the
base region 33 and is coupled out via the semiconductor columns 34.
The optically active layer in the form of the quantum well layers
is located on a surface of the semiconductor columns 34 serving as
the coupling-out structure, which is pumped by the laser light of
the primary radiation P. Thus, an efficient, scalable light source
having an adjustable color can be produced without having to use
expensive optics.
[0054] For example, the semiconductor laser 2 is a laser having a
main emission wavelength at approximately 405 nm, as used for
blu-rays. In this case, the primary radiation P is preferably
completely converted into the secondary radiation S.
[0055] Because of the wave guidance of the primary radiation P in
the semiconductor columns 34 and because of the design of the tips
35 it is achieved that the secondary radiation and/or the primary
radiation P is/are predominantly emitted in the direction parallel
or approximately parallel to the growth direction G so that a
dedicated main emission direction M results. Radiation through the
conversion element 3 is thus spatially narrower than in the case of
a Lambertian emitter.
[0056] A further exemplary embodiment is illustrated in FIG. 2. In
contrast to FIG. 1, the semiconductor columns 34 are rectangular in
cross section so that the tips 35 are oriented perpendicular to the
growth direction G. Furthermore, a mirror 5 is provided which
extends between the optional growth substrate 38, which is in
particular made of sapphire, and the carrier 4. Such a mirror 5 can
also be present in all other exemplary embodiments and is, for
example, a metallic mirror or a dielectric multilayer or
single-layer mirror or a combination of at least one dielectric
layer and at least one metal layer or semiconductor layer.
[0057] Furthermore, a luminous material 37 is additionally present
in the conversion element 3. An additional secondary radiation S2
can be generated via the luminous material 37, in particular in a
different color than the secondary radiation S directly from the
quantum well layers 31.
[0058] The luminous material 37 is formed, for example, by
inorganic phosphor particles which are embedded in a uniformly
distributed manner in a matrix material, for example, a silicone or
an epoxide. The secondary radiation S2 is preferably generated
essentially in regions above the tips 35 of the semiconductor
columns 34.
[0059] In the exemplary embodiment of FIG. 3, the quantum well
layers 31 are attached to the semiconductor columns 34, which are
shaped as a trapezoid in each case when viewed in cross section,
wherein the semiconductor columns 34 taper in the direction away
from the base region 33.
[0060] As also possible in all other exemplary embodiments, the
luminous material 37 can imitate a shape of the semiconductor
columns 34 so that a height of the luminous material 37, relative
to the base region 33, directly above the semiconductor columns 34
can be larger than in regions between the semiconductor columns 34.
In this case, a side of the luminous material 37 facing away from
the base region 33 can imitate the semiconductor columns 34 not
only exactly but also in approximation or in a smoothed manner.
[0061] Optionally, it is also possible for phosphor particles to be
present in regions between the semiconductor columns 34 in a
reduced concentration or that the phosphor particles are restricted
to a region above the tips 35.
[0062] Optionally, as in all other exemplary embodiments, a further
mirror 5b is present, in addition to the mirror 5a between the
carrier 4 and the semiconductor layer sequence 30. The mirror 5b is
oriented perpendicular to a beam direction of the primary radiation
P. The primary radiation P can be distributed more uniformly in the
base region 33 by means of the mirror 5b.
[0063] A further exemplary embodiment is illustrated in FIG. 4. As
in all other exemplary embodiments, it is possible that more than
one semiconductor laser 2 is used; according to FIG. 4, two of the
semiconductor lasers 2 are present.
[0064] The luminous material 37 is designed as a plate or platelet
having approximately plane-parallel main sides. Thus, an
intermediate space between adjacent semiconductor columns 34 is
free of the luminous material 37.
[0065] The quantum well layers 31 are located on tips of the
semiconductor columns 34 which originate from the base region 33.
Optionally, a further semiconductor material 36 is located above
the quantum well layers 31, in the direction away from the base
region 33, for example, to protect the quantum well layers 31. The
platelet with the luminous material 37 is thus either applied to
the further semiconductor material 36 or, in contrast to the
illustration in FIG. 4, is applied directly to the quantum well
layers 31. In this case, the luminous material 37 can be adhesively
bonded, for example, via a transparent, for instance
silicone-containing adhesive. Unlike in FIG. 4, a transparent,
optically non-active adhesive or residues thereof can extend into a
region between the semiconductor columns 34.
[0066] In FIGS. 1 to 4, different embodiments of the semiconductor
columns 34, of the luminous material 37 and of the mirrors 5 are
drawn. These different configurations of the individual components
can in each case be transferred to the other exemplary embodiments.
For example, the mirrors 5a, 5b from FIG. 3 can also be used in the
exemplary embodiments of FIGS. 1, 2 and 4, or the semiconductor
columns 34 from FIG. 1 can be present in FIGS. 2, 3 and 4.
[0067] In the exemplary embodiment of FIG. 5, the quantum well
layers 31 are composed of pyramid-shaped parts, similarly to napped
foam. This is achieved, for example, in that on a growth layer 32,
which is based, for example, on GaN, a mask layer 6, for instance
made of silicon dioxide, is applied. Proceeding from openings in
the mask layer 6, pyramid-shaped base regions 33 are grown, on
which the quantum well layers 31 are formed. Optionally, the
further semiconductor layer 36, for instance made of GaN, is
present, which can lead to a planarization. In other words, the
base regions are three-dimensionally grown, the quantum well layers
31 are applied to the base regions 33 true to shape, and the
further semiconductor layer 36 is a two-dimensionally grown
layer.
[0068] As in all other exemplary embodiments, it is also possible
for cladding layers 39 having a lower refractive index to be
present, in order to ensure guidance of the primary radiation P in
the direction perpendicular to the growth direction G. Optionally
present mirrors are not shown in FIG. 5. Such a mirror is
represented schematically in FIG. 6, for example.
[0069] In the exemplary embodiment of FIG. 7, deviating from FIG.
5, a roughening 7 is present on a side of the semiconductor layer
sequence 30 facing away from the growth layer 32. By means of such
a roughening 7, an emission characteristic can be influenced and a
more efficient light output can also be achieved.
[0070] In the exemplary embodiment of FIG. 8, the luminous material
37 is additionally present as a layer on the semiconductor layer
sequence 30.
[0071] FIG. 9 schematically illustrates that the conversion element
3 comprises different semiconductor columns 34 with differently
designed quantum wells. As a result, in different regions of the
conversion element 3, viewed in a plan view, secondary radiation
S1, S2, S3 having different wavelengths is emitted. It is thus
possible for mixed-colored white light to be generated by the
semiconductor light source 1, in particular composed only from the
secondary radiations S1, S2, S3.
[0072] According to FIG. 10, a mirror 5 is additionally present,
which can be designed as a Bragg mirror with a plurality of layers
with alternately high and low refractive indices. Such a mirror is
composed, in particular, of dielectric layers, and can have a
profile with regard to a reflection wavelength and can thus be
designed as a so-called chirped mirror. According to FIG. 10, the
mirror 5 covers an underside of the base region 33 facing away from
the semiconductor columns 34 and an end face of the base region 33
opposite the semiconductor laser 2.
[0073] A mirror 5 is also present in FIG. 11. The mirror 5 can be,
as in all other exemplary embodiments, a metallic reflector, for
example, with silver and/or aluminum. Possible protective layers
for the mirror 5 are not shown in FIG. 11. The mirror 5 completely
covers a bottom surface and side surfaces of the conversion element
3, with the exception of a light entrance opening for the primary
radiation P. It is optionally possible that a side of the
semiconductor columns 34 which faces away from the base region 33
is covered by the mirror 5 in a small part all around an edge.
[0074] A further exemplary embodiment is illustrated in FIG. 12. In
this case, the semiconductor laser 2 is mounted on a heat sink 81
and is contacted via electrical connections 83 out of a housing
body 82. The semiconductor light source 1 can be configured as a
so-called TO design.
[0075] The semiconductor layer sequence 30 with the semiconductor
columns 34 is arranged on a carrier 38, in particular a growth
substrate for the semiconductor layer sequence 30. The primary
radiation P is irradiated into the semiconductor layer sequence 30
in the direction parallel to the growth direction G and is
partially converted into the secondary radiation S. Thus, a mixture
of the secondary radiation S and the primary radiation P is emitted
through a light exit window 84. In contrast to the illustration,
the light exit window 894, as in all other exemplary embodiments,
can be designed as an optical element such as a lens.
[0076] According to FIG. 13, a plurality of semiconductor layers 30
having different quantum well layers 31a, 31b are present. Each of
the quantum well layers 3 1a, 31b generates a secondary radiation
S1, S2 of a particular color. Thus, mixed-colored light, which can
be free of the primary radiation P, is generated by the quantum
well layers 31a, 31b.
[0077] According to FIG. 14, an optical system 9 is located between
the semiconductor laser 2 and the conversion element 3, the optical
system 9 is preferably also present in all other exemplary
embodiments of FIGS. 12 and 13. A uniform or substantially uniform
illumination of the quantum well layers 31 with the primary
radiation P is achieved via the optical system 9. For example, the
optical system 9 is a cylindrical lens.
[0078] In the exemplary embodiment of FIG. 15, the quantum well
layers 31 are located in the base region 33 and are oriented
perpendicular to the growth direction G. In contrast to FIG. 15,
according to FIG. 16 the quantum well layers 31 are located in the
semiconductor columns 34. In this case, in particular the planar
quantum well layers 31 and a region for the subsequent
semiconductor columns 34 are first grown, only then are the
semiconductor columns 34 prepared for instance by etching. The
quantum well layers 31 can thus lie in the interior of the
semiconductor columns 34 or also below the base region 33 as a flat
quantum film.
[0079] Further, these statements with regard to the semiconductor
laser 2, the cladding layer 39, the growth substrate 38 and the
luminous material 37 to FIGS. 1 to 4 apply correspondingly to FIGS.
15 and 16.
[0080] In the semiconductor light source 1 of FIGS. 17 and 18, the
semiconductor laser 2 and the conversion element 3 are
monolithically integrated on a common growth substrate 38. In this
case, the quantum well layers 31 are located in or near a waveguide
of the semiconductor laser 2 for the primary radiation P so that as
much primary radiation P as possible can be scattered out of the
waveguide and an efficient coupling to the quantum well layers 31
takes place. The active zone 22 of the semiconductor laser 2 and
the quantum well layers 31 are preferably spatially separated from
one another in this case.
[0081] In this case, the active zone 22 of the semiconductor laser
2 in FIG. 17 is applied to a region next to the semiconductor
columns 34, viewed in a plan view. Thus, for example, the
semiconductor columns 34 arranged above the semiconductor laser 2,
along the growth direction G, are removed, but preferably not the
base region 33. In contrast to the illustration, a gap can be
located between the semiconductor laser 2 and the conversion
element 3, in order to optimize resonator mirrors of the
semiconductor laser 2, for example.
[0082] FIG. 18 shows that the active zone 22 of the semiconductor
laser 2 also extends continuously over the conversion element 3 so
that the quantum well layers 31 and the active zone 22 are stacked
one on top of the other. For better electrical contacting, the base
region 33 can be removed in the area next to the semiconductor
columns 34, in contrast to FIG. 17. It is possible that a
generation of the primary radiation P is also restricted to the
area next to the semiconductor columns 34, viewed in a plan view,
analogously to FIG. 17.
[0083] FIG. 19 shows that the semiconductor laser 2 is a so-called
stripe laser, also referred to as a ridge laser. The primary
radiation P is emitted linearly. In this case, the line on the
conversion element 3 runs perpendicular to the growth direction G
of the semiconductor layer sequence 30. A corresponding arrangement
is preferably also selected in conjunction with the exemplary
embodiments of FIG. 1 to 11, 15 or 16.
[0084] FIG. 20 shows further shapes of the tips 35. Such tips 35
can also be used in all other exemplary embodiments, wherein a
plurality of different tip types can be combined with one another
within a single conversion element 3.
[0085] According to FIG. 20A, the tip 35 is of rectangular design,
seen in cross section. The tip 35 has a smaller width than the
remaining part of the semiconductor column 34.
[0086] Deviating from the representations in FIG. 20, the
semiconductor columns 34 can also each have no special tips and
appear rectangular when viewed in cross section, as is illustrated,
for example, in FIG. 2, and as is also possible in all other
exemplary embodiments. The semiconductor columns 34 can thus be
formed cylindrically without a pointed structure.
[0087] In FIG. 20B it is shown that the tip 35 is triangular when
viewed in cross section, wherein a flank angle, in comparison with
FIG. 1, is relatively large so that an opening angle of the
triangle, furthest away from the base region 33, is, for example,
at most 60.degree. or 45.degree. or 30.degree.. According to FIG.
20C, a semicircular shape is present and, according to FIG. 20D, a
trapezoidal shape of the tip 35 is present.
[0088] According to FIG. 20E, the tip 35 is parabolic and has a
smaller diameter than remaining regions of the semiconductor column
34, as can also apply correspondingly in FIGS. 20B, 20C or 20D.
Finally, see FIG. 20F, the tip 35 is designed as a stepped
pyramid.
[0089] An average diameter of the semiconductor columns is
preferably at least .lamda./4n, wherein .lamda. is the wavelength
of maximum intensity of the primary radiation P and n is the
refractive index of the semiconductor columns 34. The diameter is
preferably between 5.lamda./n and 10.lamda./n. A typical diameter
can also lie at approximately 2.lamda./n. An aspect ratio of a
diameter and a height of the semiconductor columns is preferably at
most 1 or 0.5 or 0.2.
[0090] The invention described here is not restricted by the
description on the basis of the exemplary embodiments. Rather, the
invention encompasses any new feature and also any combination of
features, which includes in particular any combination of features
in the patent claims, even if this feature or this combination
itself is not explicitly specified in the patent claims or
exemplary embodiments.
* * * * *